Treatment of fibro-cement products



1950 o. H. WAECHTER TREATMENT -OF FIBRO-CEMENT PRODUCTS Filed Sept. 15, 1945 I N V EN TOR firm A. Mao/r59.

ATTGF/VEX' Patented Nov. 21, 1950 UNITED STATES PATENT OFFICE TREATMENT OF FIBRO-CEMENT PRODUCTS Otto H. Waechter, North Plainficld, N. J. Application September 15, 1945, Serial No. 616,529

(Cl. 92-41) v 3 Claims. 1

This invention relates to the treatment of fibrocement products such as shingles, sidings, and the like to condition them in respect of their moisture content prior to pressing or texturing. More particularly, the invention relates to the treatment of such products made from laminated asbestos-cement sheet material produced on a wet machine by the well known Hatschek process.

According to the Hatschek process a thin web of an aqueous mixture or slurry of Portland or hydraulic cement and asbestos or other mineral fibers, with or without other ingredients, is formed on the endless belt or blanket of a wet machine of the cylinder or Fourdrinier type. The web is carried by the belt to an accumulator drum or roll whereon it is wound, a number of times, until a laminated material of the desired thickness has been formed. The material is then slit lengthwise of the drum, removed therefrom, and spread or opened out into a fiat sheet. The sheet so produced is cut into elements such as shingles, sidings, and the like, which elements are subsequently subjected to a pressing operation to give them a finished textured or plain surface that enhancestheir appearance.

The pressing operation is performed either by means of a pressure roll or in a hydraulic press under high pressure. Where it is desired to finish the elements with a textured surface, as for example in simulation of wood grain, the periphery of the pressure roll is formed to effect the texturing by contact pressure with a surface of the elements, or the elements are formed into a stack with suitable texture plates interposed between adjacent ones and the stack is pressed to effect the texturing.

The laminated asbestos-cement sheet material, as it is removed from the accumulator drum and cut into elements, has a moisture content usually amounting to from about twenty-two to thirtyfive percent by weight. Prior to pressing or texturing the elements this normal moisture content must be substantially reduced because if the moisture content is too high deformation of the product will result in the pressing operation, while if it is toolow the product will crack.

It is necessary to effect the pressing while the material is still somewhat plastic and before the cement has fully set. Heretofore it has been the practice to form the elements into stacks, either with or without intervening plates, depending upon whether the pressing or texturing was to be done by a roll or in a press, and to allow them to become partially dry before pressing.-

That practice has been unsatisfactory not only because it is slow and entails additional handling but, more-especially, because it does not afford a positive control of the moisture content. It often happens that the elements in the middle portion of the stack retain a somewhat higher moisture content than the others. Non-uniformity of moisture content, particularly in the outer strata of the elements, at the time of pressing or texturing, results in the production of an unduly large number of rejects or seconds.

To obtain the best results it is essential that the moisture content of the elements should be uniform at the time they are pressed. I have found that at that time the moisture content should not be more than from about 15-25% by Weight- The principal objectof the invention is to provide a method of conditioning the elements to effect a positive control of their moisture content prior to pressing or texturing.

Another object is to provide a method that requires no handling of the product from the time that the sheets are removed from the accumulator drum until after the blanks have been pressed or textured, and that results in reducing the cost of production.

A further object is to provide a method whereby pressing or texturing of the product is greatly accelerated and that results in the production of products of uniform quality and appearance.

Further objects and advantages of'the inven tion will be apparent to those skilled in the art from the following description thereof.

The invention will be describedwith reference to the accompanying drawing which illustrated diagrammatically, in side elevation, a form of apparatus suitable for practicing the process.

A web of asbestos-cement, as formed on a conventional wet machine (not shown), is wound in convolutions or laminations on an accumulator drum or roll l0, disposed above on opposition roll ll, until the material on the accumulator drum has been built-up to the desired thickness. Thereupon it is stripped from the drum, opened out, and deposited on a conveyor l2 which,car ries it under a rotary cutter l3 and over a bed roll H. The cutter severs the sheet into elements of the desired size and shape.

The elements are carried from the cutter on a conveyor l5 to an endless belt or conveyor I 6 which progresses them through an elongated heating chamber l1 wherein they are conditioned by application of heat of a temperature above ordinary room temperature for a sufficient length of time to reduce their moisture content to about from fifteen to twenty-five percent by weight. The conveyor It may operat continuously or intermittently. The chamber I! may be heated by gas burners l8, electricity, radiant heat, or in any other suitable manner.

An important feature of the process consists in reducing the moisture content in the outer strata of the laminated elements uniformly prior to the application of pressure. In the conditionin step of the process temperature and time are correlative factors, that is the time or rate of progress of the elements through the heating chamber may be shortened if the temperature is raised, or it may be lengthened if the temperature is decreased. The absolute degree of temperature used is unimportant.

On leaving the heating or conditioning chamber, the elements may be carried by the conveyor l6 through a coolin section I9 where they are somewhat cooled by exposure to the air.

The elements then pass to a conveyor 20 that carries them under a pressure roll 2i and over an opposition roll 22. The face of the pressure roll 2| may be formed with a desired texture design, such as wood grain, stonework, etc., either in intaglio or relief, 50 as to impress or emboss the design on the surface of the elements. Instead of using a pressure roll any suitable press may be employed. Reduction of the moisture content results in a partial hardening of the elements to such a degree that they may be pressed without the excessive elongation or deformation that would occur if the blanks were not properly conditioned.

The pressed elements are delivered by a conveyor 23 and may then be trimmed, if necessary, packed in bundles or stacks and allowed to set and cure in the usual manner.

The process is continuous in the sense that no handling of the product is required from the time that the sheets have been stripped from the accumulator drum until after they have been conditioned and pressed. Moreover, the process is subject to definite control as to uniformity in the quality of production. In practice of the process, should it be found after the first element has been pressed that it had not been properly conditioned as toits moisture content, the temperature and/or time factors can easily be controlled to insure proper conditioning and uniformity of quality throughout the entire subsequent run.

What I claim is:

1. A process of treating asbestos-cement products which consists in continuously and successively progressing a series of cut freshly formed laminated asbestos-cement sheets having 9, moisture content of from about 22 to 35% by weight first through a heating zone to condition the sheets for pressing by heating said sheets sufllciently to reduce the moisture content from the outer laminations to about 15% by weight, then through a cooling zone of room temperature, and finally subjecting the cooled moisture conditioned sheets to pressure to form a densified asbestoscement product.

2. A process of treatin asbestos-cement products which consists in continuously and successively progressing a series of freshly formed 1aminated asbestos-cement sheets having a moisture content of from about 22% to 35% by weight first through a heating zone to condition the sheets for pressing by heating said sheets sufliciently to reduce the moisture content from the outer laminations to about 15% by weight, then through a cooling zone of room temperature, and

finally subjecting the cooled moisture conditioned sheets to rolling contact pressure to form a densified asbestos-cement product.

3. A process of treating asbestos-cement products which consists in continuously and successively progressing a series of freshly formed laminated asbestos-cement sheets havin a moisture content of from about 22% to 35% by weight first through a heating zone to condition the sheets for pressing by heating said sheets sufliciently to reduce uniformly the moisture content from the outer laminations to about 15% by weight, then through a zone of room temperature, and finally subjecting the moisture conditioned sheets to pressure to form a densified asbestos-cement product.

OTTO H. WAECH'I'ER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

